The vault is on the Norwegian island of Spitsbergen and contains almost a million packets of seeds.

When it was buried in 2008, the deep permafrost through which the vault was sunk was expected to provide ‘failsafe protection against the challenge of natural or man-made disasters’.

But soaring temperatures in the Arctic at the end of the world’s hottest ever recorded year led to melting and heavy rain, when light snow should have been falling.

Hege Njaa Aschim, from the Norwegian government, which owns the vault, said: ‘It was not in our plans to think that the permafrost would not be there and that it would experience extreme weather like that.

Sowing the seeds of the future in the Arctic Picture by Sipa Press/REX/Shutterstock)

‘A lot of water went into the start of the tunnel and then it froze to ice, so it was like a glacier when you went in.’

Fortunately the precious seeds remain safe for now at the required storage temperature of -18C.

But the breach has questioned the ability of the vault to survive as a lifeline for humanity if the event of a catastrophe.

Mrs Aschim said: ‘It was supposed to [operate] without the help of humans, but now we are watching it 24 hours a day.’